California Sea Grant College Program

Previous studies have demonstrated that gorgonians produce secondary metabolites that act as chemical defenses against predators and pathogens in the reef environment. While there have been investigations of the gorgonacea of the Western Atlantic which have shown that these organisms do contain defensive chemistry, the chemical ecology of Indo-Pacific gorgonians has not been investigated. The goal of this thesis research was to investigate the ecological role of Indo-Pacific gorgonian secondary metabolites in mediating interactions with potential predators and pathogens and to identify and describe the secondary metabolites responsible for observed activity.

This dissertation concerns Indo-Pacific gorgonian chemical defenses against predation by the generalist reef fish Thalassoma lunare and Halichoeres melanurus, and against the growth of fungi isolated from gorgonian tissues, including the known gorgonian pathogen Aspergillus sydowii. The identification and characterization of novel secondary metabolites from gorgonians is also presented in this dissertation.

The information gathered in these surveys led to projects involving gorgonian species of particular interest, with the aim of revealing the compound or compounds responsible for observed activities. Each project is described both biologically and chemically. The biological aspects described are the taxonomic identification of gorgonians and fungal strains. and the testing of extracts and pure compounds in assays. The chemical studies involve the isolation and structure elucidation of known and novel gorgonian secondary metabolites. The possible importance of specific compounds,or in some cases a class of compounds. in the chemical ecology of gorgonians is discussed.